The present invention relates to improvements in magnetic resonance imaging, and more particularly to the development of treatment regimens and guidance of surgical procedures using magnetic resonance imaging.
The ability to produce excellent images of the internal anatomical structure of living beings using nuclear magnetic resonance signals has been well established. Magnetic resonance imaging is highly sensitive to the relaxation times of the nuclei emitting a magnetic resonance signal, and different relaxation times are manifested as different contrasts within the image. The tissues within the various organs and structures of a patient exhibit markedly different relaxation times. Diseased and injured tissue changes in relaxation time relative to healthy tissue. Consequently, MRI produces very high contrast images of anatomical structure, in which injured and diseased tissues are clearly delineated from normal tissue.
It would be highly desirable to have techniques for making available high quality MRI images for use by a surgeon throughout the course of a surgical procedure in order to display the progress of the procedure. Presently, MRI has been largely constrained to pre-operative and post-operative imaging. Additionally, MRI has been used to perform MRI-guided fine-needle aspiration cytology and MRI-guided stereotactic neurosurgery. Experiments are also being carried out using MRI to monitor the delivery of laser light for medical purposes. However, none of these procedures involve continuous monitoring of the surgical procedure, including instrument guidance and control during the course of the procedure, by MRI guidance.
It would be an important advance in the art to have the capability of guiding an entire surgical procedure by reference to updated MRI images of the region of anatomy being operated upon. Many surgical procedures require a large incision for the purpose of exposing the anatomical region upon which the surgery is to be performed to the view of the surgeon. The surgical treatment aspect of the procedure, however, may be very localized and involve much less cutting of tissue or other disruption than that which is caused by the entire procedure. Thus, any techniques which reduce the amount of tissue damage necessary to reach the surgical site would be important in the field of surgical treatment.
Conventional CT scanning has limited application in guiding surgical procedures. First, limitations on patient exposure to X-ray prevents the unlimited use of CT scanning on any particular individual patient. In addition, a surgeon and other surgical team members must not be subjected to the repeated exposure to X-rays that would result with repeated operations on successive patients. Additionally, soft tissue imaging with CT scanning requires the use of contrast agents, and in many cases this would involve repeated and prolonged administration of contrast agents to the patient during the course of the surgical treatment.
CT also suffers from artifacts such as those that occur at the interface of bone and soft tissue. Additionally, MRI easily images an oblique plane of the patient so that the image plane orientation can be selected and changed during the course of the surgical procedure, as required. CT studies are limited to around the transaxial plane and might require patient repositioning for some surgical procedures. Moreover MRI also permits full three dimensional (3D) acquisition of images which is ideal for surgery by MRI guidance.
Related copending patent application, Ser. No. 07/993,072 filed Dec. 18, 1992, and commonly assigned herewith, discloses nuclear magnetic resonance magnets and apparatus which are suitable for MRI-guided surgery and discloses carrying out surgery within such magnets under MRI guidance. It would be desirable to use MRI guidance to the maximum degree possible, in order to minimize patient tissue damage which is caused only for the purpose of reaching the anatomical site where the surgery is to be carried out.
Notwithstanding the excellent image quality, resolution and contrast achieved in MRI images, the MRI technique has not become an integral part of the development of treatment regimens, and the identifying and development of therapeutic chemicals. MR imaging is presently applied like other traditional radiological techniques, for obtaining images representative of tissue structure. Magnetic resonance images of different anatomical portions of a patient are obtained, and the images are interpreted by a radiologist whose interpretations are reported back to a treating physician. For example, images of the internal structure of a patient's brain are obtained, the radiologist examines them for the presence of lesions, malformations or other pathology, and his interpretation is reported to the treating physician, e.g. a neurologist. The neurologist then determines a course of treatment based upon the radiologist's interpretation and other signs acquired by the neurologist.
It would be highly desirable to use MRI to acquire images of the actual course of a treatment, and not just tissue condition before and after drug treatment. Images obtained during the course of treatment could be used to alter a surgical procedure or drug therapy and drug dosage during the treatment. This use of MRI could find application in the selection of therapeutic chemicals and the selection of dosage, the development and modification of treatment regimens and for the verification of diagnosis accuracy.
Accordingly, it is an object of the invention to provide improved surgical instruments for use in MRI-guided surgery.
Another object of the invention is to provide improved MRI guided surgical procedures.
Another object of the invention is to provide new methods using MRI for developing treatment regimens and therapeutic chemicals.
Yet another object of the invention is to provide specific procedures for MRI guided treatment of tumors.